Prnewswire·2025-05-14 12:15Core Insights - Atossa Therapeutics has reported promising results from the Phase 2 Endocrine Optimization Pilot sub-study, demonstrating the bioactivity of low-dose (Z)-endoxifen in treating stage II/III ER+/HER2- breast cancer [1][4] Group 1: Study Results - No participants achieved a pathologic complete response (pCR), with residual cancer burden (RCB) classes indicating moderate to extensive disease [3] - The study showed a median Ki-67 suppression from 10.5% at baseline to 5% by Week 3, with 65% of patients achieving Ki-67 ≤ 10% [6] - Median functional tumor volume decreased by 77.7% from baseline to surgery, with the longest tumor diameter reduced by 36.8% [6] Group 2: Drug Profile - (Z)-endoxifen is a potent Selective Estrogen Receptor Modulator (SERM) that can inhibit and potentially degrade estrogen receptors, showing activity in resistant tumors [5] - The drug targets PKCβ1, an oncogenic signaling protein, at clinically achievable blood levels, and offers comparable or superior bone protection compared to tamoxifen [5] Group 3: Future Directions - Atossa is enrolling participants in an additional I-SPY2 cohort testing (Z)-endoxifen at a 40 mg daily dose, with top-line data expected in 2026 [4] - The company is focused on developing (Z)-endoxifen for metastatic breast cancer, supported by a growing intellectual property portfolio [8]